I would like to shut off the flow of water to my heater and I do not have a heater control valve on the car at this time. I have seen some discussion of using a plumbing ball valve to replace the original style valve, the ball valve being easier to turn. The pex style valve with barbed ends seems to be the one people suggest. Are these safe for automotive use. The temperature rating is around 200 degrees. The person at the plumbing store said not to do it. Any one have experience with this?